In the training of gunnery and bombing crews it is usually particularly expensive and difficult to practice with real shells, grenades, unguided rockets and bombs, and the like so that it is necessary to provide a method of simulating the ballistic or partly ballistic operation involved. In reality before such a crew is entrusted with the actual gunnery or bombing equipment it is necessary that the various range-finding and distance-calculating equipment become wholly familiar to them so as to avoid accidents and cut costs.
Typically in a gunnery operation the target is sighted in coarsely and a first shell is fired. The trajectory of the shell is followed and the hit or impact point determined. Thereupon the cannon or the like is reaimed, taking into account the information derived from the first shot. An experienced crew frequently can hit a given target on second or third shot but an inexperienced one often wastes a multitude of such shots before coming within adequate range of the desired target.
It is known to provide a model terrain over which an imaginary projectile is fired. Such a terrain is made on a reduced scale, 1 : 200 being used frequently. The various range finders and other devices used by the practicing crew are optically altered so as to give this reduced-scale model terrain the appearance, when viewed through these devices, of a full-scale battlefield. The ordnance piece, such as a tank gun or howitzer is set up next to this model terrain and connected to a computer. A target is chosen and the piece is aimed. The range elevation and scale azimuth are fed into the computer along with the type of shell being fired. The computer then calculates the trajectory the projectile would follow. The hit location, that is the point where the trajectory intersects the surface of the terrain, is marked on the terrain by a servocontrol such as a spotlight or the like. The crew then ascertains the position of this hit with the special range finder and resets the cannon, aiming it again and starting the operation over.
In this manner it is possible for an artillery crew to obtain a great deal of experience using their ordnance piece without the necessity of discharging many projectiles. In addition it is possible for such a crew to practice regardless of weather conditions, although even adverse weather conditions can be simulated on the model terrain. The terrain can correspond to a landscape or seascape, and virtually any type of ordnance equipment can be coupled to the computer so as to allow a crew to practice.
The considerable disadvantage of this system is that a relatively large computer must be used. Thus in a system 15 meters on a side subdivided into cubes 1 cm on a side it is necessary to feed into the computer the x, y, and z coordinates of the entire surface area of the terrain. This can require the storing of some 7,000,000 bits of information in the computer. Given a large enough computer it is then a relatively simple matter for it to calculate the trajectory of the imaginary shell being fired and ascertain which point on the trajectory corresponds to the point on the surface of the model terrain. The computer then directs the servocontrolled spotlight to illuminate that region which corresponds to the hit or impact point.
Such a large computer is inherently relatively expensive. Moreover it is an extremely time-consuming and difficult job to feed all of the coordinates of the surface area of the model terrain, which indeed represents a terrain 3 kilometers on a side, into the computer. Another considerable disadvantage of this system is that it is fully impossible to provide moving targets in the terrain as programming their paths of travel into the computer would further complicate the already considerable amount of information in the computer. Furthermore such a system is relatively inflexible as it eliminates the possibility of practicing with a two-part crew wherein one part merely aims and fires the ordnance piece while the other part of the crew sights the hit regions and communicates back the positions of the miss or hit, as is frequently the case in reality.